1. Field of the Invention
The present invention relates to a sheet paper transporting and aligning apparatus which receives a paper sheet and align it with a reference line before delivering it to a desired location. More in particular, the present invention is concerned with a copy paper aligning apparatus for use in copying machines and the like, which receives a copy paper as fed from the copy paper supply station and transport it to a transfer station, where a toner image is transferred onto the copy paper, after aligning one side edge of the copy paper with a reference line.
2. Description of the Prior Art
It is often desired to transport paper sheets or documents from one station to another. For example, in a transfer type copy machine, a quantity of copy papers are stored at a copy paper supply station and copy papers are removed one by one to be transported to a transfer station where developed or toner images formed on a photosensitive drum are transferred onto the copy paper. However, in order to carry out a proper image transfer operation, two requirements must be met. One of the requirements is the synchronism between the rotation of the photosensitive drum and the transport of a copy paper. That is, a copy paper must be transported to the transfer station with a proper timing so that the leading and trailing edges of the copy paper may properly match the front and rear boundaries of the image area on the peripheral surface of the photosensitive drum. A common practice to cope with this problem is to use a register roller, which is usually disposed in the copy paper travelling path and in front of the transfer station. The register roller is driven to rotate intermittently in synchronism with the rotation of the photosensitive drum and, therefore, the use of such a register roller enables to obtain matching between the leading and trailing edges of the copy paper and the front and rear boundaries of the image area. It should, however, be noted that such a register roller does not insure the sidewise alignment between the copy paper and the image area.
Therefore, the other requirement for proper image transfer is to align one side edge of the copy paper with a reference sideline before being brought into contact with the image area of the photosensitive drum. This sideline alignment is also important in correcting the orientation of the copy paper since the copy paper might be positioned somewhat aslantly with respect to the centerline of the copy paper travelling path. There are several prior art approaches to meet with this second requirement.
U.S. Pat. No. 3,980,296 issued on Sept. 14, 1976 to Craft et al. discloses an idea which may be applicable to meet such a requirement. That is, although this patent is not specifically directed to the sideline alignment of the copy paper before being fed to a register roller, it discloses a similar idea of copy paper alignment. This patent is purported to enhance the convenience of copying machines by insuring that all copy papers handled by the machine have a reference edge close to the operator. In order to attain this objective, it is proposed to provide an aligner 55 having several rollers 62,63,73 and 75 as best shown in FIG. 2 of this patent. However, it is to be noted that the copy paper 30 will be rotated around rollers 62 and 63 as soon as the roller 73 comes into engagement with the copy paper 30. As a result, one corner of the leading edge of the copy paper will move along the dotted line 65 and hit the front reference edge 46. This is not advantageous especially for thin or soft copy papers because the corner will be bent and it could be a cause of paper jamming. It should also be noted that the use of such a plurality of rollers will require fine adjustments, which necessarily complicates the structure, resulting in frequent occurrence of malfunctioning.
Another conventional approach for the sideline alignment is shown in FIGS. 1 through 3. The copy paper transport and aligning apparatus 100 generally comprises a pinch roller 3, a curved portion 4, a straight portion 7, a sideline reference wall 5 attached to the curved portion 4 and the straight portion 7, and inclined rollers 6. Thus, the copy papers stacked in a copy paper supply station are removed one by one by the action of pick-up rollers 2 and delivered to the pinch roller 3, which forms an inlet to the apparatus 100. The copy paper 12 then moves downward and slides along the curved portion 4. It is preferable to provide a discharging device 11 to eliminate possible charges on the copy paper 12 thereby preventing the copy paper 12 from being electrostatically stuck to the curved portion 4 or the straight portion 7. Then the copy paper 12 comes into contact with the inclined rollers 6 and the copy paper 12 is moved toward the sideline reference wall 5 due to the inclined arrangement of these rollers 6. As best shown in FIG. 2, the rollers 6 are arranged such that their axis of rotation is inclined over the angle, .theta., with respect to the line normal to the center line of the copy paper travelling path. Therefore, if the copy paper 12 is fed into the transport and aligning apparatus 100 with its edge in contact with the supply reference line 1a of the copy paper supply station 1 as shown in FIG. 2, the copy paper 12 will be moved over the distance a to abut against the sideline reference wall 5. Since the wall 5 presents a flat surface for contact with one edge of the copy paper 12, the orientation of the copy paper 12 is also adjusted. This completes the alignment procedure since the location of the reference wall 5 is previously determined with respect to the side boundary 10a of the image area defined on the photosensitive drum 10.
The register roller 8 has an idler roller and it is driven to rotate intermittently in response to the rotation of the drum 10. Thus, when the leading edge of the copy paper 12 comes into contact with the register roller 8 which is not in rotation, the advancement of the copy paper 12 is halted. On the other hand, the inclined rollers 6 are usually driven to rotate continuously. Such being the case, the inclined rollers 6 must be so arranged that they lightly touch the surface of the copy paper 12. In other words, the rollers 6 must impart a force on the copy paper 12 strong enough to move it toward the sideline reference wall 5, but the force must be weak enough for the rollers 6 to slip on the surface of the copy paper 12 while its advancement motion is restrained by engagement with the register roller 8. When the register roller 8 initiates its rotation, the copy paper 12 is advanced toward the transfer station 9 where the toner image formed on the photosensitive drum 10 is transferred onto the copy paper 12.
The distance L.sub.1 between the pinch roller 3 and the inclined rollers 6 and the distance L.sub.2 between the inclined rollers 6 and the register roller 8, both measured along the copy paper travelling path, should be shorter than the length between the leading and trailing edges of the smallest copy paper used, e.g., B5 size in FIG. 2. Furthermore, the total distance, L.sub.1 +L.sub.2, should be set to the sum of the length between the leading and trailing edges of the largest copy paper used and the distance which is necessary and sufficient for the largest copy paper to be aligned with the sideline reference by means of the inclined rollers after its trailing edge leaving the pinch roller 3.
As shown in FIG. 2, the supply reference line 1a is usually defined at the distance a inside of the sideline reference wall 5. This is because the copy paper 12 might change its orientation during advancement along the travelling path due to unexpected vibrations or the like, and, even if it happens, this arrangement can allow the copy paper to stay within the limits of the travelling path, thereby avoiding the occurrence of jamming.
However, this prior art technique still suffers from disadvantages. For example, if the copy paper 12 is oriented as shown by the one-dot line in FIG. 3 immediately before the inclined rollers 6, the corner 12a of the copy paper 12 will first hit the sideline reference wall 5 as shown by the two-dot line. The frictional force working between the wall 5 and the corner 12a tends to bend the corner 12a and, more in severe cases, the copy paper 12 is jammed. This is more true for thinner or softer copy papers.